1. Field of the Invention
The invention refers to a method for the production of a membrane comprising selectively gas-permeable windows.
2. Description of the Prior Art
Selectively gas-permeable membranes are needed in measuring and analysis apparatuses in order to separate certain gases from other gases and to determine the presence of the interesting gases. A typical field of application of such membranes are leak detectors which detect a tracer gas flowing from a leak. Typical tracer gases are, among others, helium and hydrogen, which are light gases and pass through membranes that cannot be passed by heavier gases.
EP 0 831 964 B1 (Leybold Vacuum GmbH, =U.S. Pat. No. 6,277,177 B1) describes a selective gas passage formed by a plate of a silicon material such as quartz, quartz glass, Pyrex glass, silicon oxide, silicon nitride, silicon oxynitride, or silicon carbide, which is supported on a silicon disc with a plurality of windows. The windows have been made by structured etching of the silicon disc from the rear and they are covered by a thin membrane. Each of the windows is provided with a helical heating element for local heating of the gas passage. This structure of a gas-selective membrane is complex.